A comparison of a traditional and wavefront autorefraction

An Innovative Virtual Reality System for Measuring Refractive Error

In this study, we aimed to validate a novel light field virtual reality (LFVR) system for estimating refractive errors in the human eye. Fifty participants with an average age of 22.12 ± 2.2 years (range 20-30 years) were enrolled. The present study compared spherical equivalent (SE) and focal line measurements (F1 and F2) obtained by the LFVR system with those obtained by established methods, including closed-field and open-field autorefractors, retinoscopy, and subjective refraction. The results showed substantial agreement between the LFVR system and the traditional methods, with intraclass correlation coefficients (ICC) for SE ranging from 82.7% to 86.7% (p < 0.01), and for F1 and F2 from 80.7% to 86.4% (p < 0.01). Intra-repeatability for F1 and F2 demonstrated strong agreement, with ICC values of 88.8% and 97.5%, respectively. These findings suggest that the LFVR system holds potential as a primary tool for refractive error measurement in optical care, offering high agreement and repeatability compared to conventional methods.

Clinical Evaluation Of a 0.05 D-step Binocular Wavefront Optometer in Young Adults in China

CLINICAL RELEVANCE

Myopia has become a public health priority as its prevalence increases worldwide, and in clinical practice, the precise evaluation of refraction errors is necessary.

BACKGROUND

This study aimed to compare objective and subjective refraction measured by a binocular wavefront optometer (BWFOM) in adults with conventional objective and subjective refractions measured by an optometrist.

METHODS

This cross-sectional study included 119 eyes of 119 participants (34 men and 85 women; mean age:27.5 ± 6.3 years). Refractive errors were measured using BWFOM and conventional methods, with and without cycloplegia. The mean outcome measures were spherical power, cylindrical power, and spherical equivalence (SE). The agreement test was assessed using a two-tailed paired t-test and Bland - Altman plots.

RESULTS

Under noncycloplegic conditions, there were no significant differences in the objective SE between BWFOM and Nidek. Significant differences in subjective SE were observed between BWFOM and conventional subjective refraction (-5.79 ± 1.86 vs -5.65 ± 1.75 D, P < 0.01). Under cycloplegic conditions, the mean objective SE was significantly different between BWFOM and Nidek (-5.70 ± 1.76 vs -5.50 ± 1.83 D, P < 0.001); the mean subjective SE was significantly different between BWFOM and conventional subjective refractions (-5.52 ± 1.77 vs -5.62 ± 1.79 D, P < 0.001). The Bland - Altman plots revealed mean percentages of 95.38% and 95.17% for the points within the limits of agreement between BWFOM and conventional measurements and those between noncycloplegic and cycloplegic refractions, respectively.

CONCLUSION

The BWFOM is a new device that measures both objective and subjective refraction. It is more convenient and faster to obtain a proper prescription at a 0.05-D interval. The subjective refraction results of the BWFOM and the conventional subjective refraction were in good agreement.

Repeatability and Interobserver Reproducibility of a Swept-Source Optical Coherence Tomography for Measurements of Anterior, Posterior, and Total Corneal Power

INTRODUCTION

The aim of this work is to evaluate the intraobserver repeatability and interobserver reproducibility of corneal power measurements obtained with a swept-source optical coherence tomographer (CASIA 2, Tomey, Japan) in healthy subjects.

METHODS

A total of 67 right eyes from 67 healthy subjects were enrolled. Two experienced observers measured each eye three times consecutively with the CASIA 2. Corneal power values were recorded as simulated keratometry, anterior, posterior, and total corneal power. Parameters were flattest keratometry (Kf), steepest keratometry (Ks), mean keratometry (Km), astigmatism magnitude, astigmatism power vectors J0 and J45. Intraobserver repeatability and interobserver reproducibility of the CASIA 2 were assessed by the within-subject standard deviation (Sw), test-retest repeatability (TRT), coefficients of variation (CoV), and intraclass correlation coefficients (ICCs). Double-angle plots were used for astigmatism vector analysis.

RESULTS

The CASIA 2 had high repeatability for all corneal power values, with Sw values ≤ 0.17 diopters (D), TRT ≤ 0.46 D, and ICCs ranging from 0.866 to 0.998. Interobserver reproducibility was also high, showing all Sw values ≤ 0.10 D, TRT ≤ 0.27 D, and ICCs ≥ 0.944. The reproducibility of the average of three consecutive measurements (Sw 0.01-0.10 D, TRT 0.03-0.27 D, ICC 0.944-0.998) was higher than the reproducibility of single measurements (Sw 0.01-0.17 D, TRT 0.03-0.47 D, ICC 0.867-0.996).

CONCLUSIONS

The CASIA 2 showed high intraobserver repeatability and interobserver reproducibility for anterior, posterior, and total corneal power measurements in 6.0-mm diameter area. In addition, we suggest that using the average of three consecutive measurements can improve reproducibility between observers, compared to single measurements only.

Effect of six different autorefractor designs on the precision and accuracy of refractive error measurement

PURPOSE

To evaluate the precision of objective refraction measurements with six different autorefractors that have different designs and measurement principles and to compare the objective refraction values with the subjective refraction.

METHOD

Objective refraction of 55 participants was measured using six autorefractors with different designs. The instrument features mainly varied in terms of measurement principles, inbuilt fogging, open or closed view, and handheld or stationary designs. Two repeated measurements of objective refraction were performed with each autorefractor. The objective refractions from the six autorefractors were compared with the standard subjective refraction. The repeatability limit and Bland-Altman were used to describe the precision and accuracy of each autorefractor, respectively. The analysis was done using the spherical component of the refraction and the power-vector components, spherical equivalent (M), and cylindrical vectors.

RESULTS

The repeatability of all autorefractors was within 1.00 and 0.35D for measuring the M and both cylindrical components, respectively. Inbuilt fogging was the common feature of the instruments that showed better repeatability. Compared to subjective refraction, the mean difference for sphere and M was below +0.50D, and it was close to zero for the cylindrical components. The instruments that had inbuilt fogging showed narrower limit of agreement. When combined with fogging, the open field refractors showed better precision and accuracy.

CONCLUSIONS

The inbuilt fogging is the most important feature followed by the open view in determining the precision and accuracy of the autorefractor values.

Repeatability of i.Profiler for measuring wavefront aberrations in healthy eyes

PURPOSE

To evaluate the repeatability of wavefront aberration measurements and the correlation between corneal aberration and pupil size in normal eyes using a wavefront-based autorefractor (i.Profiler^Plus; Carl Zeiss Vision, Germany).

METHODS

A prospective cross-sectional study. Wavefront aberrations, including spherical aberration (SA) (Z₄⁰), coma (Z₃^-1, Z₃¹), trefoil (Z₃^-3, Z₃³) and total higher-order aberrations (tHOA), were measured at different pupil diameters. The repeatability was evaluated using one-way ANOVA method, and statistical indicators including within-subject standard deviation (S_w), test-retest repeatability (TRT), and intra-class correlation coefficient (ICC). The correlations between corneal aberrations and pupil sizes were evaluated by Pearson correlation analysis.

RESULTS

A total of 96 healthy young volunteers were enrolled. Corneal and ocular higher-order aberrations (HOA) measured by i.Profiler showed S_w < 0.01 μm, TRT < 0.10 μm, ICC > 0.90. There was a linear positive correlation between the corneal HOA and pupil size. The correlation coefficient between SA and tHOA was the largest (r = 0.996, P < 0.001).

CONCLUSIONS

The measurements of wavefront aberrations by i.Profiler are highly repeatable. Corneal HOA was significantly dependent on pupil size. SA was the most influential aberration for visual quality in this study.

Predicting subjective refraction with dynamic retinal image quality analysis

The aim of this work is to evaluate the performance of a novel algorithm that combines dynamic wavefront aberrometry data and descriptors of the retinal image quality from objective autorefractor measurements to predict subjective refraction. We conducted a retrospective study of the prediction accuracy and precision of the novel algorithm compared to standard search-based retinal image quality optimization algorithms. Dynamic measurements from 34 adult patients were taken with a handheld wavefront autorefractor and static data was obtained with a high-end desktop wavefront aberrometer. The search-based algorithms did not significantly improve the results of the desktop system, while the dynamic approach was able to simultaneously reduce the standard deviation (up to a 15% for reduction of spherical equivalent power) and the mean bias error of the predictions (up to 80% reduction of spherical equivalent power) for the handheld aberrometer. These results suggest that dynamic retinal image analysis can substantially improve the accuracy and precision of the portable wavefront autorefractor relative to subjective refraction.

Effects of varying illumination on ocular aberrations and aberration compensation before and after small incision Lenticule extraction: a prospective cohort study

BACKGROUND

There are few reports regarding the influence of varying illumination on the compensation effect before and after corneal refractive surgery. We aimed to evaluate the changes in refraction, higher-order aberrations, and aberration compensation between mesopic and photopic illumination before and after small incision lenticule extraction.

METHODS

In this prospective cohort study, only the right eyes of patients who underwent small incision lenticule extraction for the correction of myopia and myopic astigmatism at the Tianjin Eye Hospital were included. Wavefront refraction and higher-order aberrations were measured preoperatively and 3 months postoperatively under mesopic and photopic illumination. Compensation factors were calculated as 1 - (aberration of the whole eye/aberration of the anterior corneal surface).

RESULTS

Forty patients undergoing small incision lenticule extraction were enrolled. All surgeries were completed without postoperative complications. Preoperatively, the eyes only had a statistically significantly higher (t = - 4.589, p < .001) spherical refractive error under mesopic vs. photopic illumination (median [interquartile range], - 6.146 [2.356] vs. - 6.030 [2.619] diopters [D]), whereas postoperatively, the eyes also exhibited statistically significantly higher (t = - 3.013, p = .005) astigmatism (- 0.608 [0.414] vs. - 0.382 [0.319] D). Differences in spherical refraction between the two illuminations were the highest in postoperative eyes (Δ > 0.5 D). Only postoperative eyes exhibited statistically significant elevations (t ≥ 4.081, p < .001) in higher-order aberrations under mesopic illumination, and only preoperative eyes exhibited statistically significantly enhanced (χ² = 6.373, p = .01 for fourth-order and χ² = 11.850, p = .001 for primary spherical aberrations) and decreased (χ² = 13.653, p = .001 for horizontal trefoil) compensation factors under mesopic illumination.

CONCLUSIONS

Exaggerations in higher-order aberrations and myopic shift after small incision lenticule extraction became apparent under mesopic illumination. Slight undercorrection may have an enhanced effect under low illumination and may reduce night vision. The specific changes in compensation effects in preoperative eyes may improve optical quality under mesopic illumination. Postoperative eyes have reduced compensation ability, specifically for spherical aberrations, under mesopic illumination, which may diminish night vision. Further studies that include the measurement of subjective night vision parameters should be conducted.

The Precision of a New Anterior Segment Optical Coherence Tomographer and Its Comparison With a Swept-Source OCT-Based Optical Biometer in Patients With Cataract

PURPOSE

To assess the precision of a new spectral-domain optical coherence tomographer (SD-OCT)/Placido topographer (MS-39; CSO) and its comparison with a swept-source OCT (SS-OCT) biometer (Argos; Movu, Inc) in patients with cataract.

METHODS

Fifty-three right eyes from 53 patients were examined by two experienced operators three times using both devices randomly. Employing the within-subject standard deviation (S_w), test-retest variability, coefficient of variation, and intraclass correlation coefficient to evaluate intraoperator repeatability and interoperator reproducibility; the double-angle plots to analyze astigmatism; and Bland-Altman plots and 95% limits of agreement to verify the agreement between devices.

RESULTS

The SD-OCT/Placido tomographer showed high precision, with coefficient of variation of 0.44% or less, intraclass correlation coefficient of 0.945 or greater for all parameters, test-retest variability of 4.21 µm or less for central corneal thickness (CCT), 0.03 mm or less for anterior chamber depth (ACD) and aqueous depth (AQD), and 0.25 diopters (D) or less for mean keratometry (Km), J₀, and J₄₅. The inter-device differences in Km, J₀, and J₄₅ were statistically insignificant, whereas the remaining were statistically but not clinically significant. The 95% limits of agreement of CCT, ACD, AQD, Km, J₀, and J₄₅ were -3.70 to 15.25 µm, -0.06 to 0.04 mm, -0.06 to 0.04 mm, -0.28 to 0.35 D, -0.27 to 0.26 D, and -0.27 to 0.21 D, respectively. The double-angle plot confirmed the high agreement in astigmatism.

CONCLUSIONS

For CCT, ACD, AQD, Km, and astigmatism measurements in patients with cataract, the new SD-OCT/Placido tomographer has excellent precision and high agreement with the Argos SS-OCT biometer, and can be used interchangeably. [J Refract Surg. 2021;37(9):616-622.].

Clinical Reliability of IOL Master 700 in Measurement of Pupil Diameter and Corneal Curvature

Purpose: To compare IOL Master 700 with autokeratometer and video pupillometer in measurement of pupil diameter and corneal curvature.Methods: Pupil diameter were measured with IOL Master 700 and video pupilometer, horizontal keratometry and vertical keratometry were measured with IOL Master 700 and autokeratometer in 100 eyes of 50 children. Paired t-test and Pearson's correlation analysis were used to compare the differences among the devices. Agreement between measurement was analyzed using Bland Altman plot and intraclass correlation coefficient.Results: Comparing IOL Master 700 and video pupilometer for pupil diameter, there was no significant difference (p > 0.05). There was also no significant difference between IOL Master 700 and autokeratometer in measurement of vertical keratometry (p > 0.05). However, regarding horizontal keratometry there was significant difference between IOL Master 700 and autokeratometer, horizontal keratometry measured with IOL Master 700 was steeper than with auto keratometer, +0.105 diopters (D) in right eye and +0.130 D in left eye (p < 0.05).Conclusions: There was good agreement between IOL Master 700 and comparator instruments in regards to pupil diameter and corneal curvature. IOL Master 700 can be helpful in uncooperative children for measuring pupil diameter and corneal curvature at the same time.

Agreement and variability of subjective refraction, autorefraction, and wavefront aberrometry in pseudophakic patients

PURPOSE

To evaluate the comparability and variability of subjective refraction (SR), autorefraction (AR), and wavefront aberrometry (WA) in pseudophakic patients.

SETTING

Hanusch Hospital, Vienna, Austria.

DESIGN

Prospective study.

METHODS

Subjective refraction was performed by 2 independent examiners at 2 study visits. Furthermore, 5 measurements of AR and WA were performed in each patient at both visits. Agreement between the 3 refraction methods for spherical equivalent (M) and cylindrical vectors (J0, J45) was analyzed using Friedman multiple comparison and Bland-Altman plots. Predictability of spherical equivalent determined by SR from AR and WA measurements was tested with partial least squares regression and random forest regression.

RESULTS

Ninety eyes of 90 pseudophakic patients were measured. The mean absolute error and arithmetic mean difference of SR measurements of M, J0, and J45 were comparable between both examiners. A small mean difference was found for SR between both visits. Spherical equivalent was more negative when measured by AR [-0.87 diopters (D)] and WA (-0.90 D) compared with SR (-0.60 D), whereas astigmatic vectors agreed well. Good test-retest reliability was found between all 3 refraction methods for M, J0, and J45. Partial least squares regression and random forest regression showed moderate predictive power for M measured by objective refraction and SR.

CONCLUSIONS

Reproducibility and reliability of SR measurements in pseudophakic patients showed good agreement. AR and WA measured the spherical equivalent more myopic than SR, whereas astigmatic vectors were comparable between the 3 methods after uneventful cataract surgery.

V. SD, Nagaraj S, Wittberg DM, Stamper RL, Keenan JD. Accuracy of autorefraction in an adult Indian population

Purpose

Autorefractors allow non-specialists to quickly assess refractive error, and thus could be a useful component of large-scale vision screening programs. In order to better characterize the role of autorefraction for public health outreach programs in resource-limited settings, the diagnostic accuracy of two autorefractors was assessed relative to subjective refraction in an adult Indian population.

Methods

An optometrist refracted a series of patients aged ≥50 years at an eye clinic in Bangalore, India using the Nidek ARK-900 autorefractor first, followed by the 3nethra Royal autorefractor, and then subjective refraction. The diagnostic accuracy of each autorefractor for myopia, hyperopia, and astigmatism was assessed using subjective refraction as the reference standard, and measures of agreement between refractions were calculated.

Results

A total of 197 eyes in 104 individuals (mean age 63 ± 8 years, 52% female) were evaluated. Both autorefractors produced spherical equivalent estimates that were on average more hyperopic than subjective refraction, with a measurement bias of +0.16 D (95%CI +0.09 to +0.23D) for Nidek and +0.42 D (95%CI +0.28 to +0.54D) for 3nethra. When comparing pairs of measurements from autorefraction and subjective refraction, the limits of agreement were approximately ±1D for the Nidek autorefractor and ±1.75D for the 3Nethra autorefractor. The sensitivity and specificity of detecting ≥1 diopter of myopia were 94.6% (95%CI 86.8–100%) and 92.5% (95%CI 88.9–97.5%) for the Nidek, and 89.2% (95%CI 66.7–97.4) and 77.5% (95%CI 71.2–99.4%) for the 3Nethra. The accuracy of each autorefractor increased at greater levels of refractive error.

Conclusions

The sensitivity and specificity of the Nidek autorefractor for diagnosing refractive error among adults ≥50 years in an urban Indian clinic was sufficient for screening for visually significant refractive errors, although the relatively wide limits of agreement suggest that subjective refinement of the eyeglasses prescription would still be necessary.

A Comparison Between Refraction From an Adaptive Optics Visual Simulator and Clinical Refractions

Purpose

The Visual Adaptive Optics (VAO) is an adaptive optics visual simulator with an embedded Hartmann–Shack aberrometer that can give objective and subjective refraction measures. The aim of the present study was to compare the findings of the objective and subjective refractions from the VAO with a commercial autorefractometer (Topcon Corp., Tokyo, Japan) and a subjective refraction by an optometrist. The influence of age, refractive error type, and presence of ocular diseases was ascertained.

Methods

The refractive error was obtained in 469 participants using the four techniques mentioned. Data were analyzed with power vectors mean spherical equivalent, the vertical Jackson-Cross-Cylinder, and the oblique Jackson-Cross-Cylinder. Age, refractive error type (myopia, emmetropia, hyperopia) and presence of ocular diseases (yes, no) were included as covariates. Agreement was assessed using the 95% interval of agreement.

Results

The median spherical equivalent difference and the interval of agreement for all the participants with the VAO subjective, VAO objective, and autorefraction with the clinical subjective refraction were (+0.13, 1.80 diopters [D]), (+0.38, 1.80 D), and (−0.38, 2.10 D), respectively. When considering only healthy participants, the results were (+0.06, 1.70 D), (+0.38, 1.60 D) and (−0.25, 1.80 D), respectively. When considering only those participants with any ocular condition, the results with VAO subjective, VAO objective and autorefraction were (+0.13, 2.50 D), (+0.31, 2.70 D), and (−0.50, 4.80 D), respectively.

Conclusions

The VAO subjective refraction is more accurate than VAO objective refraction and autorefraction, regardless of refractive error, age, or the presence of ocular conditions. The presence of ocular conditions significantly deteriorates the accuracy of all refraction methods.

Translational Relevance

Reported clinical comparisons between different types of standard refraction methods and a new adaptive optics refraction instrument (VAO) are in good agreement and support the further development of this method to increase refraction accuracy and to refract quicker than standard procedures.

Advancing Digital Workflows for Refractive Error Measurements

Advancements in clinical measurement of refractive errors should lead to faster and more reliable measurements of such errors. The study investigated different aspects of advancements and the agreement of the spherocylindrical prescriptions obtained with an objective method of measurement ("Aberrometry" (AR)) and two methods of subjective refinements ("Wavefront Refraction" (WR) and "Standard Refraction" (StdR)). One hundred adults aged 20-78 years participated in the course of the study. Bland-Altman analysis of the right eye measurement of the spherocylindrical refractive error (M) identified mean differences (±95% limits of agreement) between the different types of measurements of +0.36 D (±0.76 D) for WR vs. AR (t-test: p < 0.001), +0.35 D (± 0.84 D) for StdR vs. AR (t-test: p < 0.001), and 0.0 D (± 0.65 D) for StdR vs. WR (t-test: p < 0.001). Monocular visual acuity was 0.0 logMAR in 96% of the tested eyes, when refractive errors were corrected with measurements from AR, indicating that only small differences between the different types of prescriptions are present.

Reference curves for refraction in a German cohort of healthy children and adolescents

PURPOSE

Percentile curves of refractive development for German children were generated. We hypothesize that refraction in children in central Europe might differ from data in central Asia.

METHODS

Non-cycloplegic refraction was measured using the ZEISS i.Profiler plus (Carl Zeiss Vision GmbH, Germany) in 1999 children, of which were 1046 male and 953 female, aged 3 to 18 years. Reference curves were calculated with the R-package GAMLSS as continuous function of age.

RESULTS

There were only little differences for all centiles between the genders at 3 years and a general trend towards more myopia with increasing age. For the 97th centile and the 3rd centile, girls showed higher myopia/ less hyperopia than boys. Between the age of 3 and 18, the median refraction became -0.68 D and -0.74 D more myopic for boys and girls, respectively. At the same time, the 97th centile for boys changed +0.29 D towards hyperopia and in girls -0.52 D towards myopia. A general myopic trend was seen in the 3rd centile, which was -2.46 D for boys and -2.98 D for girls. For both genders, the median became less than zero at the age of 10 years but did not become myopic (less than -0.5 D) up to the age of 18.

CONCLUSION

Our analysis presents the first reference curve for refraction in central Europe. In comparison to data from China and Korea, there is only little difference at the age of 5 years in all centiles which then increases continuously. For all ethnicities, a trend towards myopia with increasing age could be observed, but myopia progression is much higher in China and Korea than in Germany. The most marked differences can be seen in the lower centiles. Further investigations should clarify whether commencement of preschool activities with prolonged near-work initiates the divergence in refractive development.

Agreement and Repeatability of Noncycloplegic and Cycloplegic Wavefront-based Autorefraction in Children

SIGNIFICANCE

Increasing prevalence of refractive error requires assessment of ametropia as a screening tool in children. If cycloplegia is not an option, knowledge about the increase in uncertainty for wavefront-based autorefraction is needed. The cycloplegic agent as the principal variant presents cross-reference and allows for extraction of the influence of accommodation.

PURPOSE

The purpose of this study was to determine the repeatability, agreement, and propensity to accommodate of cycloplegic (ARc) and noncycloplegic (ARnc) wavefront-based autorefraction (ZEISS i.Profiler plus; Carl Zeiss Vision, Aalen, Germany) in children aged 2 to 15 years.

METHODS

In a clinical setting, three consecutive measurements were feasible for 145 eyes (OD) under both conditions. Data are described by spherical equivalent (M), horizontal or vertical astigmatic component (J0), and oblique astigmatic component (J45). In the case of M, the most positive value of the three measurements was chosen, whereas the mean was applied for astigmatic components.

RESULTS

Regarding agreement, differences for ARc minus ARnc were statistically significant: for M, 0.55 (0.55 D; mean [SD]; P < .001), that is, more hyperopic in cycloplegia; for J0, −0.03 (0.11 D; P = .002); and for J45, −0.03 D (SD, 0.09 D; P < .001). Regarding repeatability, astigmatic components showed excellent repeatability: SD < 0.11 D (ARnc) and SD < 0.09 D (ARc). The repeatability of M was SD = 0.57 D with a 95% interval of 1.49 D (ARnc). Under cycloplegia, this decreased to SD = 0.17 D (ARc) with a 95% interval of 0.50 D. The mean propensity to accommodate was 0.44 D from repeated measurements; in cycloplegia, this was reduced to 0.19 D.

CONCLUSIONS

Wavefront-based refraction measurement results are highly repeatable and precise for astigmatic components. Noncycloplegic measurements of M show a systematic bias of 0.55 D. Cycloplegia reduces the propensity to accommodate by a factor of 2.4; for noncycloplegic repeated measurements, accommodation is controlled to a total interval of 1.49 D (95%). Without cycloplegia, results improve drastically when measurements are repeated.

Validation of an Affordable Handheld Wavefront Autorefractor

SIGNIFICANCE

There is a critical need for tools that increase the accessibility of eye care to address the most common cause of vision impairment: uncorrected refractive errors. This work assesses the performance of an affordable autorefractor, which could help reduce the burden of this health care problem in low-resource communities.

PURPOSE

The purpose of this study was to validate the commercial version of a portable wavefront autorefractor for measuring refractive errors.

METHODS

Refraction was performed without cycloplegia using (1) a standard clinical procedure consisting of an objective measurement with a desktop autorefractor followed by subjective refraction (SR) and (2) with the handheld autorefractor. Agreement between both methods was evaluated using Bland-Altman analysis and by comparing the visual acuity (VA) with trial frames set to the resulting measurements.

RESULTS

The study was conducted on 54 patients (33.9 ± 14.1 years of age) with a spherical equivalent (M) refraction determined by SR ranging from -7.25 to 4.25 D (mean ± SD, -0.93 ± 1.95 D). Mean differences between the portable autorefractor and SR were 0.09 ± 0.39, -0.06 ± 0.13, and 0.02 ± 0.12 D for M, J0, and J45, respectively. The device agreed within 0.5 D of SR in 87% of the eyes for spherical equivalent power. The average VAs achieved from trial lenses set to the wavefront autorefractor and SR results were 0.02 ± 0.015 and 0.015 ± 0.042 logMAR units, respectively. Visual acuity resulting from correction based on the device was the same as or better than that achieved by SR in 87% of the eyes.

CONCLUSIONS

This study found excellent agreement between the measurements obtained with the portable autorefractor and the prescriptions based on SR and only small differences between the VA achieved by either method.

Comparison of Two Wavefront Autorefractors: Binocular Open-Field versus Monocular Closed-Field

Purpose

To evaluate the agreement and repeatability between a new commercially available binocular open-field wavefront autorefractor, as part of the Eye Refract system, and a monocular closed-field wavefront autorefractor (VX110).

Methods

A cross-sectional, randomized, and single-masked study was performed. Ninety-nine eyes of 99 healthy participants (37.22 ± 18.04 years, range 8 to 69 years) were randomly analyzed. Three measurements with the Eye Refract and the VX110 were taken on three different days, under noncycloplegic conditions. Mean spherical equivalent (MSE), cylindrical vectors (J0 and J45), and binocular corrected distance visual acuity (BCDVA) were compared between both autorefractors. An intersession repeatability analysis was done considering the values of repeatability (S_r) and its 95% limit (r).

Results

The VX110 showed more negative values (P < 0.001) in terms of MSE in comparison with the Eye Refract (0.20 D). Regarding cylindrical vectors, J45 showed statistically significant differences (P=0.001) between both wavefront autorefractors, but they were not clinically relevant (<0.05 D). In BCDVA, there were no statistically significant differences (P=0.667) between both wavefront autorefractors. Additionally, the Eye Refract was more repeatable than the VX110 in terms of both MSE (S_{rEYE REFRACT} = 0.21 D, S_rVX110 = 0.53 D) and J0 (S_{rEYE REFRACT} = 0.12 D, S_rVX110 = 0.35 D).

Conclusions

The Eye Refract provided enough accuracy and reliability to estimate refractive errors in different age groups, achieving better results than the VX110. Therefore, the Eye Refract proved to be a useful autorefractor to be incorporated into clinical practice.

Accuracy of a Smartphone-based Autorefractor Compared with Criterion-standard Refraction

SIGNIFICANCE

Uncorrected refractive error is a prevalent problem throughout the world especially among the low-income population who have limited access to professional eye care and cannot afford eyeglasses.

PURPOSE

The purpose of this study was to evaluate the accuracy and usability of a low-cost, portable, smartphone-based autorefractor (Netra, EyeNetra Inc., Somerville, MA) in adults.

METHODS

A cross-sectional study was conducted to compare the portable refractor with subjective (manifest and cycloplegic) refraction for sequential adult participants with best-corrected visual acuity of 20/40 or greater. For each method of refraction, the spherical equivalent was calculated. Differences between methods were tested with linear mixed regression models. A validated usability questionnaire was administered regarding ease of use (100-point scale, higher scores better) for the portable autorefractor.

RESULTS

Eighty-seven subjects (152 eyes) were studied (age range, 20 to 90 years; mean ± standard deviation, 51.9 ± 18.3 years). Mean spherical equivalent by the portable device was -2.76 D (range, -14.75 to 3.63 D) compared with -2.49 D (range, -15.25 to 4.25 D) by manifest refraction. The mean relative difference in spherical equivalent between methods was -0.27 D (P = .001, significantly different than 0 D). The mean absolute difference between methods was 0.69 D (P < .001, significantly different than 0.5-D absolute difference). Similar results were found when comparing spherical equivalent between Netra and cycloplegic refraction methods. Subjects reported average ease of use for the Netra of 75.4 ± 19.8.

CONCLUSIONS

The portable autorefractor had small but clinically significant differences from subjective refraction. The device's scores on the usability scale indicate good overall patient acceptance. The device may be valuable for use where there is limited access to a trained refractionist.

Comparing habitual and i. Scription refractions

BACKGROUND

Many patients voice concerns regarding poor night vision, even when they see 20/20 or better in the exam room. During mesopic and scotopic conditions the pupil size increases, increasing the effects on visual performance of uncorrected (residual) refractive errors. The i.Scription refraction method claims to optimize traditional refractions for mesopic and scotopic conditions, by using the information that the Zeiss i.Profilerplus gathers of ocular aberrations (low and high order). The aim of this study was to investigate any differences between habitual and i.Scription refractions and their relationship to night vision complaints.

METHODS

Habitual, subjective, and i.Scription refractions were obtained from both eyes of eighteen subjects. Low and high order aberrations of the subjects were recorded with the Zeiss i.Profilerplus. The root mean square (RMS) metric was calculated for small (3 mm) and maximum pupil sizes. Subjects rated their difficulty with driving at night on a scale of 1-10.

RESULTS

There was a statistically significant difference between the habitual and i.Scription refractions on both the sphere and cylinder values [(t = 3.12, p < 0.01), (t = 5.39, p < 0.01)]. The same was found when comparing the subjective and i.Scription refractions [(t = 2.31, p = 0.03), (t = 2.54, p = 0.02)]. There were no significant differences found when comparing the sphere and cylinder values between the habitual and subjective refractions or on any combination of spherical equivalent refraction. The maximum pupil size of the subject population on this study, measured with the i.Profilerplus, was 4.8 ± 1.04 mm. Ten out of the eighteen subjects had discomfort at night with an average magnitude of 4 ± 2.7. Ratings of difficulty with night vision correlated with the change in spherical equivalent correction between the habitual and i.Scription refractions (p = 0.01). A sub-analysis of myopic subjects (n = 15) showed an increase in the significance of this relationship (p = 0.002).

CONCLUSIONS

The i.Scription method improves night vision by correcting the sphere and cylinder more precisely. There was a correlation between the amount of change in the cylinder value between habitual and i.Scription prescriptions and the magnitude of the reported visual discomfort at night.

Assessment of subjective refraction with a clinical adaptive optics visual simulator

PURPOSE

To clinically validate an adaptive optics visual simulator (VAO) that measures subjective refraction and visual acuity.

SETTING

Optics Laboratory, University of Murcia, Murcia, Spain.

DESIGN

Prospective case series.

METHODS

Using the adaptive optics visual simulator, 2 examiners measured the subjective refraction and visual acuity in healthy eyes of volunteers; 1 examiner also used a trial frame as a gold standard. The interexaminer reproducibility and agreement with the gold standard were estimated using the following statistical parameters: limits of agreement from Bland-Altman analysis, significance between differences (P value), and intraclass correlation coefficient (ICC).

RESULTS

Seventy-six eyes of 38 volunteers were measured. Interexaminer reproducibility for subjective refraction was excellent (ICC ≥0.96; P > .05), with low 95% confidence interval (CI) values for the power vectors M (spherical equivalent of the given refractive error), J0 (Jackson cross-cylinder, axes at 180 degrees and 90 degrees), and J45 (Jackson cross-cylinder, axes at 45 degrees and 135 degrees) (±0.51 diopter [D], ±0.14 D, and ±0.14 D, respectively). No significant differences in subjective refraction and visual acuity were found between the visual simulator and gold standard (P > .05), with 95% CIs for M, J0, and J45 (subjective refraction) of ±0.67 D, ±0.14 D, and ±0.16 D, respectively, and a ±0.10 logarithm of the minimum angle of resolution (visual acuity).

CONCLUSION

Subjective refraction results using the adaptive optics visual simulator agreed with those of the gold standard and can be used as the baseline for visual simulation of any optical corneal profile or intraocular lens design for refractive surgery patients.

Comparison Between Aberrometry-Based Binocular Refraction and Subjective Refraction

Purpose

We evaluate the efficacy of a new system of binocular refraction, mainly based on ocular aberrometry (EYER) and compare it with the traditional subjective refraction as gold standard.

Methods

A prospective, double blind, and transversal study was performed on 99 subjects (35 men, 64 women; mean age 37.22 ± 18.04 years; range, 7–70 years). Refractive surgery or irregular cornea were considered exclusion criteria. Subjective refraction was performed by three different optometrists and EYER by other optometrists on three different days randomly. The binocular best corrected visual acuity (BBCVA), subjective vision evaluated with visual analogue scale (VAS), refraction spent time, and mean spherical equivalent (MSE), and vertical and oblique cylindrical components (J0 and J45) were analyzed.

Results

A positive strong correlation between EYER and subjective refraction was found for MSE (Pearson, 0.984; P < 0.001) and J0 and J45 (Pearson, 0.837; P < 0.001 and Pearson, 0.852; P < 0.001, respectively) in the total group. There were no statistically significant differences for BBCVA (P < 0.05). The VAS scores were 84.29 ± 12.29 with the EYER and 86.89 ± 12.38 with subjective refraction (P = 0.031). The spent time to perform the refraction was statistically lower (P < 0.05) with the EYER compared to conventional subjective refraction for all groups.

Conclusions

The EYER system showed similar results in terms of spherical and cylindrical components, visual acuity being the spent time in the refraction lower than conventional subjective refraction.

Translational Relevance

This new objective refraction system provides less chair spent time with similar results than subjective refraction.

New Objective Refraction Metric Based on Sphere Fitting to the Wavefront

Purpose

To develop an objective refraction formula based on the ocular wavefront error (WFE) expressed in terms of Zernike coefficients and pupil radius, which would be an accurate predictor of subjective spherical equivalent (SE) for different pupil sizes.

Methods

A sphere is fitted to the ocular wavefront at the center and at a variable distance, t. The optimal fitting distance, t_opt, is obtained empirically from a dataset of 308 eyes as a function of objective refraction pupil radius, r₀, and used to define the formula of a new wavefront refraction metric (MTR). The metric is tested in another, independent dataset of 200 eyes.

Results

For pupil radii r₀ ≤ 2 mm, the new metric predicts the equivalent sphere with similar accuracy (<0.1D), however, for r₀ > 2 mm, the mean error of traditional metrics can increase beyond 0.25D, and the MTR remains accurate. The proposed metric allows clinicians to obtain an accurate clinical spherical equivalent value without rescaling/refitting of the wavefront coefficients. It has the potential to be developed into a metric which will be able to predict full spherocylindrical refraction for the desired illumination conditions and corresponding pupil size.

Effect of Pupil Size on Wavefront Refraction during Orthokeratology

PURPOSE

It has been hypothesized that central and peripheral refraction, in eyes treated with myopic overnight orthokeratology, might vary with changes in pupil diameter. The aim of this work was to evaluate the axial and peripheral refraction and optical quality after orthokeratology, using ray tracing software for different pupil sizes.

METHODS

Zemax-EE was used to generate a series of 29 semi-customized model eyes based on the corneal topography changes from 29 patients who had undergone myopic orthokeratology. Wavefront refraction in the central 80 degrees of the visual field was calculated using three different quality metrics criteria: Paraxial curvature matching, minimum root mean square error (minRMS), and the Through Focus Visual Strehl of the Modulation Transfer Function (VSMTF), for 3- and 6-mm pupil diameters.

RESULTS

The three metrics predicted significantly different values for foveal and peripheral refractions. Compared with the Paraxial criteria, the other two metrics predicted more myopic refractions on- and off-axis. Interestingly, the VSMTF predicts only a marginal myopic shift in the axial refraction as the pupil changes from 3 to 6 mm. For peripheral refraction, minRMS and VSMTF metric criteria predicted a higher exposure to peripheral defocus as the pupil increases from 3 to 6 mm.

CONCLUSIONS

The results suggest that the supposed effect of myopic control produced by ortho-k treatments might be dependent on pupil size. Although the foveal refractive error does not seem to change appreciably with the increase in pupil diameter (VSMTF criteria), the high levels of positive spherical aberration will lead to a degradation of lower spatial frequencies, that is more significant under low illumination levels.

Day 1 wavefront aberrometry for prediction of refractive outcomes at year 1 in myopic LASIK

PURPOSE

To determine amount of change in wavefront aberrometric measurements from 1 day to 1 year after myopic LASIK.

METHODS

One hundred five eyes of 105 patients underwent wavefront-guided LASIK. Objective wavefront aberrometric refractions were recorded preoperatively, at postoperative day 1, and at postoperative year 1. Subjective manifest refractions were also collected at postoperative year 1.

RESULTS

When comparing objective wavefront aberrometric refractions at postoperative year 1 to postoperative day 1, there was a mean 0.33 diopter spherical equivalent myopic shift. There was no significant difference in the number of eyes within 1.00 diopter of emmetropia spherical equivalent measured by wavefront aberrometric refraction at postoperative day 1 or year 1. There was a correlation of R(2) = 0.14 between degree of preoperative myopia and myopic shift. Higher-order aberrations were overall not increased at day 1 but increased significantly by year 1. Objective aberrometric refractions at postoperative day 1 can be useful in prediction of long-term refractive outcomes.

CONCLUSIONS

There is a small myopic shift and an increase in higher-order aberrations when comparing wavefront aberrometry results at postoperative day 1 with those at postoperative 1 year.